The present invention relates to semiconductor devices and, more particularly, to those encapsulated in cases with a metallic support and a body of synthetic resin. A case of metal and resin frequently used in the production of integrated power circuits is that known under the name "Multiwatt", which is a registered trademark of the applicant. It includes a metallic plate incorporated in part into a body of synthetic resin in such a way as to leave free a larger surface. A semiconductor element chip, in which an integrated circuit is formed and which constitutes the active part of the device, is affixed to the other larger surface of the plate in intimate thermal contact therewith so as to enable the transmission to the outside, and thereby the dissipation, of heat generated by the semiconductor element chip during the operation thereof. Rigid metal conductors acting as terminals of the device are connected via thin wires to metallized zones of the semiconductor element chip and are in part incorporated into the body of resin and in part protrude therefrom, all aligned along the same side.
In the mass production of devices of this kind, the metallic plates intended for a large number of identical devices are obtained, usually by die cutting, from a relatively thick sheet metal, e.g., copper, and remain joined together in series of 10-20 pieces by means of a tab of sheet metal. Similarly, the rigid metal conductors are obtained, by die cutting or by chemical etching, from a thinner sheet metal, e.g., copper, and remain joined together by transverse metal sections. The strip of the plates and that of the conductors are then joined together, e.g., by some of the rigid conductors that are properly folded and seamed in appropriate notches of the plates; a semiconductor element chip is affixed to each plate, for example by brazing, are welded onto appropriate metallized zones of the chip and onto the conductor tips in order to make appropriate electrical connections between the active element of the device and its terminals. Everything is then inserted into an appropriate mold and into this mold is introduced, by pressure injection, a resin which is in the liquid state, e.g., a thermosetting polymer. After the resin has hardened, the individual devices are separated by die cutting both the tabs that held the plates together and the sections of sheet metal that held the rigid conductors together.
In many cases, the need for increasingly complex circuits capable of coping with increasingly higher powers has forced designers to give up integrating the entire circuit in a single semiconductor element chip in favor of solutions that called for the use of two or more chips. A typical case is that of a circuit having one portion with signal processing functions integrated into a first chip, and one portion with power functions integrated into a second chip. Usually however, circuit users do not want to abandon maximum compactness, that is to say, to have the entire circuit in a single case regardless of the number of chips necessary for its production. However, this forces a person making such devices in many cases to design a new type of case and corresponding costly modifications of the processes of production, or even to create new appropriate lines of production. This proves necessary, especially if the circuit is made of chips in which base electrodes must be insulated from each other.